Digital receivers such as DTV receivers requires channel estimation for later processing. In addition, digital receivers are known to use an equalizer such as decision-feedback equalizers (DFE). The use of DFE in digital demodulation is known.
However, DFE equalization is not suitable for enabling the initial acquisition of digital modulation that is severely distorted by multipath-induced intersymbol interference. Therefore, a reference waveform or reference sequence is typically introduced.
In the United States, an 8-level vestigial sideband modulation (8-VSB) is proposed for the terrestrial broadcast of digital television transmission by the Advanced Television Systems Committee ATSC. The 8-level vestigial sideband modulation is a special single carrier technique. As in most wireless transmission, multipath propagation is one of the major challenging problems in VSB signal transmission. Multipath propagation degrades the receiver performance by introducing inter-symbol interference (ISI). Often, time-domain decision-feedback equalization (DFE) is required. U.S. Pat. No. 7,230,983 to Yousef describes a DFE means for determine coefficients of a decision feedback equalizer from a sparse channel estimate. However, the result of the equalization is not used for later channel estimation purposes.
U.S. Pat. No. 5,886,748 to Lee describes an Equalizing method and equalizer using reference signal. However, the cited work does not address the multipath issues relevant to ATSC DTV reception.
In summary, previous work concentrates on continuous adaptive DFE and is not suited for mobile application. For a receiver in a mobile context such a moving automobile, channel conditions may change at a rate greater than that of a non-mobile context. Therefore, it is desirous to have a mobile receiver equalizer structure that possesses an improved means for modeling channel conditions.